Our understanding of the neural mechanisms of memory has been advanced by the characterization of neural activity in behaving animals. The research described in the Projects 2-3 depends crucially on sophisticated devices for simultaneous recording of the activity of multiple neurons and field potentials at multiple sites. For some aims, we require that these devices give us the flexibility to sample hippocampal neurons with regular spacing along the septotemporal axis. For the last aim of Project 3, we require the ability to deliver patterned electrical stimulation to neurons at flexibly chosen sites. Development and fabrication of these devices will be accomplished by establishment of a dedicated facility and personnel who will design and construct multichannel electrode arrays, as well as headstages for preliminary amplification and stimulation of neural activity at multiple sites. The Engineering Core will also serve as a general electronics and mechanics shop for Center personnel and students. Engineering Core personnel will train Center members in safe use of Core equipment and serve as a source of technical advice.